"Excelsior" is one of Sam Loyd´s most famous chess problems, originally published in London Era in 1861, named after the poem "Excelsior" by Henry Wadsworth Longfellow. Loyd bet a friend that he could not pick a piece that didn´t give mate in the main line, and when it was published it was with the stipulation that white mates with "the least likely piece or pawn".